Single-phase electric motors are typically equipped with a starting winding to improve starting torque and reduce a starting time. Once the motor reaches a running speed, the starting winding must be disconnected.
In the past mechanical devices have been used to disconnect the starting winding.
Typically a weight moved by centrifugal force is suspended from a lever which is, in turn, attached to a rotor of the motor. As the motor gains speed, the weight pressed against the lever forcing it outwards against a spring. As the motor reached full speed the force causes the lever to contact and activate a switch which disconnects the starting winding.
While the prior art mechanical devices have worked relatively well, they are prone to mechanical failure. They also require significant space due to the necessary mechanical movement. Because of the importance of single-phase motors, a need exists for a means for disconnecting starting windings that does not suffer from the deficiencies of the prior art.